Sinking Clouds

Normally, clouds rise in the sky. Water vapor in the air condenses to form droplets of water or ice. Usually the condensation is around microscopic dust particles. Cloud movement may be helped by warm air moving up from the ground. But not all clouds move up.

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A mammatus cloud is an unusual formation usually seen after a severe thunderstorm. They do not indicate a coming tornado, although many people believe this. Mammatus clouds represent a rare example of a sinking cloud.

Sometimes the cloud has a high concentration of droplets and ice particles, making it heavier that the air around it. This higher density causes the cloud to sink. As the cloud sinks, it will warm and the particles in it will start to evaporate. If more energy is needed for evaporation than is produced by the drop in altitude, the cloud will continue to sink.